Centering coupling for splined shafts submersible pumping systems and electrical submersible pumps

ABSTRACT

A submersible pumping system, electrical submersible pump, and method of providing enhanced alignment of motor and driven shafts of submersible pumping systems and electrical submersible pumps, are provided. An example of an electrical submersible pump system includes a pump, a pump motor, and a seal section. The motor drives the pump via motor and driven shafts rotatingly coupled with a coupling assembly. The coupling assembly maintains the shaft ends in coaxial alignment with an alignment device. The alignment device is profiled on opposite ends for mating engagement with the centering guides extending from the shaft ends.

RELATED APPLICATIONS

This application is a continuation of and claims priority to and the benefit of U.S. patent application Ser. No. 13/657,986, filed Oct. 23, 2012, which is a continuation of and claims priority to and the benefit of U.S. patent application Ser. No. 12/332,717, filed Dec. 11, 2008, now abandoned, which is a continuation-in-part of and claims priority to and the benefit of U.S. patent application Ser. No. 12/125,350, filed May 22, 2008, now abandoned, each incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to electrical submersible well pumps, and in particular to couplings between splined shafts of submersible pumping systems and methods of providing enhanced alignment of motor and driven shafts of submersible pumping systems and electrical submersible pumps.

2. Description of the Related Art

Electrical submersible pumps (ESP) are commonly used for hydrocarbon well production, FIG. 1 provides an example of a submersible pumping system 10 disposed within a wellbore 5. The wellbore 5 is lined with casing 4 and extends into a subterranean formation 6. Perforations 9 extend from within the wellbore 5 through the casing 4 into the formation 6. Hydrocarbon fluid flow, illustrated by the arrows A, exits the perforations 9 into the wellbore 5, where it can either be pumped by the system 10 or migrate to a wellhead 12 disposed on top of the wellbore 5. The wellhead 12 regulates and distributes the hydrocarbon fluid for processing or refining through an associated production line 7.

The pumping system 10 includes an electrical submersible pump (ESP) 14 with production tubing 24 attached to its upper end. The ESP 14 comprises a motor 16, an equalizer or seal 18, a separator 20, and a pump 22. A fluid inlet 26 is formed in the housing in the region of the ESP 14 proximate to the separator section 20. The fluid inlet 26 provides a passage for the produced hydrocarbons within the wellbore 5 to enter the ESP 14 and flow to the pump 22. Fluid pressurized by the pump 22 is conveyed through the production tubing 24 connecting the ESP 14 discharge to the wellhead 12. The pump 22 and separator 20 are powered by the motor 16 via a shaft (not shown) that extends from the motor 16. The shaft is typically coupled to respective shafts in each of the pump 22, separator 20, and seal 14.

Delivering the rotational torque generated by an ESP motor 16 typically involves coupling a motor shaft (i.e., a shaft connected to a motor or power source) to one end of a driven shaft, wherein the other end of the driven shaft is connected to and drives rotating machinery. Examples of rotating machinery include a pump, a separator, and tandem pumps. One type of coupling comprises adding splines on the respective ends of the shafts being coupled and inserting an annular collar over the splined ends, where the annular collar includes corresponding splines on its inner surface. The rotational force is well distributed over the splines, thereby reducing some problems of stress concentrations that may occur with keys, pins, or set screws. Examples of a spline cross-section include an involute and a square tooth. Typically, splines having an involute cross-section are smaller than square tooth splines, thereby leaving more of the functional shaft diameter of a shaft to carry a rotational torque load. Additionally, involute spline shapes force the female spline to center its profile on the male spline, thus coaxially aligning the shafts in the coupling with limited vibration. Square tooth splines are made without specialized cutters on an ordinary mill. However, square teeth spline couplings do not align like involute teeth unless the clearance is reduced or the male and female fittings are forced together. However, reducing clearance or force fitting square teeth splines prevents ready assembly or disassembly.

SUMMARY OF THE INVENTION

In view of the foregoing, various embodiments of the present invention provide a submersible pumping system for pumping wellbore fluid, which advantageously provides for alignment of square teeth spline couplings, without requiring clearance to be reduced or the male and female fittings to be forced together.

According to an example of an embodiment of the invention, a submersible pumping system is provided which includes a pump motor, a motor shaft having a splined end positioned within one end of the shaft coupling, and a driven shaft having a splined end positioned within an opposite end of the shaft coupling opposite to the motor shaft. The driven shaft is driven by the motor shaft via the splined shaft coupling. At least one, but typically both the driven shaft and the motor shaft include centering guides extending from a face of a terminal end of the respective shaft. The system also includes an alignment element positioned within the shaft coupling. The alignment element includes at least one, but more typically a pair of opposite oriented coaxial centering profiles. According to an exemplary configuration, the body of the alignment element has a disk-like shape, and each centering profile is bored into opposite sides of the body of the alignment element. The pair of centering guides coaxially engage the centering profiles extending into the body of the alignment element to provide for dynamic aligning of the respective shafts. The pair of centering guides can comprise a pair of conically shaped protrusions extending from the axially facing surfaces of the terminal ends of the motor and driven shafts. As a result of such configuration, the splined ends of the motor shaft and driven shaft are held substantially coaxial within the splined shaft coupling during rotation, even when manufacturing has placed them at the outer limits of normal tolerances for square tooth splined shaft couplings. Also, according to such configuration, the splined ends of the motor and driven shafts can be easily separated from within the splined shaft coupling to allow for ready assembly and disassembly. Additionally, according to an exemplary configuration, the shaft coupling has a shoulder formed in the splined shaft coupling. Additionally, the system includes a threaded sleeve secured within the splined shaft coupling. The threaded sleeve is positioned in contact with the disk portion of the alignment element, with the disk portion being secured between the shoulder and the sleeve.

Various embodiments of the present invention also provide an electrical submersible pump (ESP) systems. An example of an electrical submersible pump includes a pump, a pump motor, an equalizer or seal section connected between the pump and the pump motor, a motor shaft mechanically affixed to the pump motor, and a driven shaft driven by the motor shaft. The motor shaft has a splined end portion including a plurality of elongate square tooth spines formed thereon, and has a terminal end portion including a tapered centering guide extending therefrom, being coaxial with an axis of the motor shaft. The driven shaft has a splined end portion including a plurality of elongate square tooth spines formed thereon, and has a terminal end portion including a tapered centering guide extending therein, being coaxial with an axis of the driven shaft. A splined shaft coupling assembly rotatingly couples the splined ends of the motor shaft and the driven shaft. An alignment element is mounted in portions of the splined shaft coupling assembly. The alignment element includes a tapered centering profile on one side that mates with the tapered centering guide extending from the motor shaft, and a tapered centering profile on an opposite side that mates with the tapered centering guide extending from the driven shaft. According to an exemplary configuration, the tapered centering guides and the tapered centering profiles are conical and of substantially same dimensions.

Various embodiments of the present invention also include methods of providing enhanced alignment of motor and driven shafts of a submersible pumping system having male square tooth splined ends. This is advantageously performed without reducing clearance between male and female square tooth splines or force fitting the male square tooth splines within the female square tooth splines. Such methods can provide for ready assembly or disassembly of the splined ends of a motor shaft and driven shaft from within a splined shaft coupling. An example of such a method can include the steps of providing a centering guide on each splined shaft end, mounting an alignment element within a splined shaft coupling configured for rotatingly coupling respective splined ends of the motor shaft and the driven shaft, and inserting the splined shaft ends into the splined shaft coupling and engaging oppositely oriented centering profiles on the alignment element with the inner surfaces of the centering guides on the splined shaft end. To facilitate engagement of the centering profiles with the centering guides to thereby maintain coaxial alignment of the shaft ends, each centering profiles can comprise a conically shaped protrusion and each centering guide can comprise a conically shaped recess to provide a conically shaped entrance.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features and advantages of the invention, as well as others which will become apparent, may be understood in more detail, a more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only various embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it may include other effective embodiments as well.

FIG. 1 is a side view of a prior art submersible electrical pumping system in a wellbore.

FIG. 2 a is an exploded view of a shaft coupling for use with the system of FIG. 1.

FIG. 2 b is an assembled view of the shaft coupling of FIG. 2 a.

FIG. 3 a is an exploded view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 3 b is an assembled view of the shaft coupling of FIG. 3 a.

FIG. 4 a is an exploded view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 4 b is an assembled view of the shaft coupling of FIG. 4 a.

FIG. 5 is a side partial cut-away view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 6 is a side partial cut-away view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 7 is a perspective view of an embodiment of an alignment member.

FIG. 7A is an end sectional view of the alignment member of FIG. 7.

FIG. 8 is a side partial sectional view of the alignment member of FIG. 7 engaged with opposing shafts.

FIG. 9 is a perspective view of an embodiment of a tolerance ring.

FIG. 10 is a side partial sectional view of the tolerance ring of FIG. 9 disposed between a shaft and a shaft coupling.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

The present disclosure includes a description of a submersible pumping system including a square tooth spline coupling with vibration control. The coupling disclosed herein provides sufficient clearance between the respective male and female splines providing ready assembly and disassembly. With reference now to FIG. 2 a, an exploded side partial cutaway view of one embodiment of a coupling assembly and respective shafts is provided. As noted above, during operation of a pumping assembly, a motor shaft is powered by a pump motor, either directly or through a shaft coupling. The coupling assembly provides a manner of connecting the motor shaft to a driven shaft that drives rotating machinery. The coupling connection also transfers rotational energy between the motor and driven shaft, thus providing power for the rotating machinery. Thus with respect to couplings described herein, the term motor shaft includes any shaft mechanically coupled to the motor that is being coupled to a driven shaft. As such, embodiments exist where one end of a rotating shaft is a driven shaft coupled to a motor shaft and the other end of the rotating shaft is a motor shaft coupled to a driven shaft. Accordingly, ESP systems may include the couplings of the present disclosure at any shaft connection within the system and ESP systems may include multiple couplings of the present disclosure.

The coupling assembly 30 of FIG. 2 a comprises an annular collar 48 with a bore 50 formed lengthwise therein. Female splines 52 extend axially along the bore 50 inner surface. The bore 50 diameter transitions at a point to form a shoulder 56 that is substantially perpendicular to the collar 48 axis A_(X). An alignment element 54 is on the shoulder 56. In the embodiment shown, the alignment element 54 has a disc-like midsection and disposed in the collar 48 with its midsection axis (not shown) largely aligned with or parallel to the collar axis A_(X). The alignment element 54 outer diameter exceeds the shoulder 56 inner diameter and its lower side abuts on the shoulder 56. The outer diameter fits closely in the bore 50. An insert or sleeve 60 is coaxially received within the collar 48 in the portion of the bore 50 having an increased diameter. The insert 60 extends from the upper surface of the alignment member 54 terminating at the upper end of the collar 48. The insert 60 is optionally threaded on its outer diameter to mate with corresponding threads provided on the collar 48 inner diameter. Female splines 52 are formed along the insert 60 inner diameter. Positioning the insert 60 against the alignment element 54 toward the shoulder 56, retains the alignment element 54 within the collar 48.

Centering guides (62, 63) are shown extending from the upper and lower surface of the alignment element 54. In this embodiment, the centering guides (62, 63) comprise conically shaped protrusions. Above and below the coupling assembly 30 are an upper shaft 32 and lower shaft 40. The upper shaft 32 lower end 36 is provided with male splines 34 configured for coupling engagement with the female splines 52 of the coupling assembly 30. Similarly, the lower shaft 40 upper end 44 includes male splines 42 configured for coupling engagement with the female splines 52. The shafts (32, 40) are profiled on their terminal ends for centering engagement with the centering guides (62, 63) of the alignment element 54. In the embodiment shown, the profiling on the shafts comprises recesses or bores (38, 46) extending from the terminal mating tips of the shafts and substantially aligned with the respective axes (A_(SH), A_(SL)) of the upper or counterbore lower shafts (32, 40). Each recess (38, 46) has a conical entry way with a taper matching the centering guides (62, 63). The recess and protrusion provide examples of guide profiles formed on the shaft ends and alignment element for engaging the shaft ends to the alignment element. During pumping operations, impellers in the pump create an axial thrust force in the pump shaft forcing the shafts (32, 40) together and engaging the centering guides (62, 63) with the recesses (38, 46).

Referring now to FIG. 2 b, an example of an assembled shaft coupling is shown in side cross-sectional view. The male splines 34 on the lower end 36 of the upper shaft 32 engage the female splines 52 and the upper shaft 32 bore 38 mates with the centering guide 62 that extends from the alignment element 54. Similarly, the male splines 42 on the upper end 44 of the lower shaft 40 are engaged with the female splines 52 of the collar 48 and the bore 46 on the upper terminal end of the shaft 40 mates with the centering guide 63 that extends from the opposite side of the alignment element 54. The upper shaft 32 and lower shaft 40 are aligned along a common axis within the collar 48 thus preventing shaft vibration when one of the shafts energizes the other.

FIG. 3 a shows an alternative embodiment of a shaft coupling 30 a for coupling an upper shaft 36 a to a lower shaft 44 a. In this embodiment, the alignment element 54 a has a largely disc-like cross-sectional area and is seated on the shoulder 56. The insert 60 retains the element 54 a within the collar 48. The centering guides (62 a, 63 a) comprise a conical profile bored into the body of the alignment element 54 a. Similarly, the terminal tips of the upper shaft 36 a and lower shaft 44 a include conically profiled protrusions (39, 47) formed to engaged the bores of the centering guides (62 a, 63 a). FIG. 3 b illustrates the assembled shaft coupling 30 a and engagement of the protrusions (39, 47) with the centering guides (62 a, 63 a). This configuration also controls shaft vibration during transmission of torque through the coupling 30 a. The profiles on the alignment elements and the terminal tips of the shafts are not limited to the figures described herein, but can include other shapes such as conical, concave, convex, spherical or other curved surfaces. Additionally, cylindrical profiles with may be employed and may include rounded tips on the cylinder end.

Yet another embodiment of a shaft coupling 30 b is provided in side cross-sectional view in FIG. 4 a. In this embodiment, the centering guides 62 b and centering guide 63 b comprise a raised profile on the respective upper and lower sides of the alignment element 54 b. The alignment element 54 b comprises an upper housing 64, a lower housing 66, and a resilient member housed within the upper and lower housings (64, 66). One example of a resilient member is a spring 68. In this embodiment, the upper and lower housing (64, 66) both comprise a generally cup-like structure having a closed base that is largely perpendicular to the axis of the collar 48 a. The housings have sides extending from the base towards an open end; the sides lie generally concentric with the axis A_(X) of the collar 48 a. The upper housing 64 inner diameter is greater than the lower housing 66 outer diameter allowing insertion of the lower housing 66 into the upper housing 64 in telescoping relation. The spring 68 provides a resilient force for urging the upper and lower housing (64, 66) apart.

As shown in FIG. 4 b, in some embodiments, a vertical force may move the shaft (32, 40) toward one another and pushes on one of the upper or lower housing (64, 66), thereby compressing the spring 68 there between. One of the advantages of this embodiment is an axial force from one of the shafts (32, 40) is fully absorbed by the spring 68 and not transferred to the other or any other adjacent shaft within a pumping system. Moreover, the resilient nature of the spring 68 can force the housings (64, 66) apart upon absence of the vertical force while continuing axial alignment of the shafts (32, 40) during operation of the pumping system. Because rotational shafts in an ESP seal portion typically are not subjected to axial thrust, the resilient feature may be useful for these couplings. As shown, the housings (64, 66) have protrusions profiled on their respective outer surfaces formed to match recesses (38, 46) on the shafts (32, 40). However, the housings (64, 66) could be fashioned to include recesses and the shafts (32, 40) having corresponding protrusions.

Another embodiment illustrating ESP shaft coupling is provided in a side partial cut-away view in FIG. 5. Here an upper shaft 36 b and lower shaft 44 b are aligned with a retaining pin 70 that extends from a bore 38 b in the lower terminal end of the upper shaft 36 b into a corresponding bore 46 b in the upper terminal end of the lower shaft 44 b. The retaining pin 70 may include an annular shoulder 71 radially disposed around the body of the pin 70 approximately at its mid-section. To accommodate the retaining pin 70, the bores (38 b, 46 b) are formed deeper into the shafts (36 b, 44 b) than the bores (38, 46) illustrated in FIGS. 2 a and 2 b.

A coupling assembly is presented in side partial cross sectional view in FIG. 6 that combines concepts described above. An upper shaft 36 with a bore 38 is disposed within a collar 48 b into coaxial alignment with a corresponding lower shaft 44 b. A protrusion 47 a extends from the lower shaft 44 b upper terminal end into the bore 38 and is retained therein for coaxial alignment of the shafts (36, 44 b). The protrusion 47 a of FIG. 6 is similar to the protrusion 47 of FIGS. 3 a and 3 b, but has increased dimensions, including an increased length, to ensure mating cooperation with the bore 38. The collar 48 b inner diameter is smaller at its upper end to match the upper shaft 36 outer diameter. The collar 48 b can be machined or forged as a uni-body configuration, or reduced with an insert (not shown) similar to the collar 48 of FIGS. 2 a-3 b.

An example of an alternative shaft coupling is provided in FIGS. 7 and 8. FIG. 7 depicts split pin 74 in perspective view. The embodiment of the split pin 74 illustrated is an elongated member having a substantially cylindrical shaped body 75, however the split pin 74 can also have cross sectional shapes with multiple sides. In the embodiment of FIG. 7, a vertical slot 76 initiates from a first end 77 of the body 75 extending through the body 75 to a vertical terminal end 78. Projecting from the body 75 second end 79 is a horizontal slot 81 that extends past the vertical terminal end 78 to a horizontal terminal end 83. FIG. 7 illustrates the first end 77 in forward looking view depicting an optional filler material 80 inserted within the slot 76. The filler material 80 should compress to allow pin 74 insertion and may include a fiber type material, such as cotton, felt, or fiberglass. Other materials include foam, cork, polymers, elastomeric polymers, and the like.

With reference now to FIG. 8, an example of a shaft coupling is provided in a side partial sectional view. Here an embodiment of the split pin 74 is coaxially disposed between an upper end 44 b and a lower end 36 b. Similar to the embodiment of FIG. 5, the split pin 74 has an end extending into the bore 38 b of the lower end 36 b and an opposite end extending into the bore 46 b of the upper end 44 b. The pin 74 ends can have an outer dimension approximately the same or greater than the bores 38 b, 46 b. The slots 76, 81 enable the ends 77, 79 to be compressed and inserted within the bores 38 b, 46 b. Forming the split pin 74 from an elastic material, such as steel, results in the pin 74 ends outwardly pushing against the inner circumference of the bores 38 b, 46 b; this couples the pin 74 to the ends of the shafts. The bores 38 b, 46 b being substantially aligned with the respective shaft axes shaft, provides alignment of the shaft ends 38 b, 44 b during use when the split pin 74 is coupled with the bores 38 b, 46 b.

Another optional compressive alignment element is illustrated in FIGS. 9 and 10. With reference to FIG. 9, an annular sleeve 82 is shown in perspective view. The annular sleeve 82 is a tubular member having a corrugated outer peripheral surface formed by protrusions 84 extending therefrom. Optionally, the protrusions 84 may extend from the sleeve 82 inner surface, or from both the inner and outer surfaces. The protrusions 84 are preferably formed from an elastic material, such as steel, that is able to be deformed and then return to its previous shape and also exert a resistive force while in the deformed state. An example of an annular sleeve 82 suitable for use as herein disclosed is a tolerance ring, that may be purchased from Rencol, 85 Route 31 North, Pennington, N.J. 08534, Tel: 609-745-5000, Fax: 609-745-5012, www.usatolerancerings.com.

FIG. 10 illustrates a side partial sectional view of a shaft 86 having splines 87 formed on the end of the shaft 86. An optional collar 88 is depicted on the end of the shaft 86, having on its inner circumference a corresponding profile of splines 89 for mating with the splines 87 on the shaft 86. A pin 85 is pictured inserted into bores 91, 92 formed on the ends of the shafts 86, 90 to align and stabilize the shafts 86, 90 during rotation. An embodiment of the annular sleeve 82, with protrusions 84, circumscribes the pin 85 ends to enhance coupling stability between the pin 85 and bores 91, 92. The protrusions 84 on the annular sleeve 82 are in temporary deformable compression when the pin 85 is in the bores 91, 92. The elasticity of the protrusions 84 couples the pin 85 within each bore 91, 92 thereby aligning the ends of the shafts 86, 92. As shown, two annular sleeves 82 are provided on each pin 85 end, but other arrangements are possible. For example, a pin 85 may have a single sleeve 82 on one end with a pair of sleeves 82 on its opposite end. Embodiments exist with more than two sleeves 82 on an end of a pin 85.

The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. 

That claimed is:
 1. A submersible pumping system for pumping wellbore fluid, comprising: a pump motor; a pump; a splined shaft coupling; a motor shaft having a splined end positioned within one end of the splined shaft coupling, the motor shaft having a terminal end, the splined end comprising a plurality of elongate square tooth splines; a driven shaft having a splined end positioned within an opposite end of the splined shaft coupling opposite to the motor shaft, the splined end comprising a plurality of elongate male square tooth splines, the driven shaft having a terminal end, one or both of the terminal ends of the motor shaft and the driven shaft comprising a centering guide individually extending therefrom, the driven shaft being driven by the motor shaft via the splined shaft coupling; a substantially cylindrically shaped annular insert positioned within the splined shaft coupling to retain the alignment element within a counter bore of the splined shaft coupling, the insert comprising a plurality of elongate female square tooth splines formed along an inner diameter of a bore extending through the insert, the elongate female square tooth splines configured for coupling engagement with the elongate male square tooth splines; and an alignment element landed within the splined shaft coupling, the alignment element having a pair of oppositely oriented faces, a body extending therebetween, and one or more centering profiles each separately extending into the body of the alignment element through a separate one of the pair of opposite faces, the one or more centering profiles coaxially receiving the one or more centering guides correspondingly extending from one or more of the terminal ends of the motor and driven shafts when operably positioned within the shaft coupling.
 2. The submersible pumping system as defined in claim 1, wherein the terminal end of the motor shaft and the terminal end of the driven shaft each separately comprise a centering guide extending therefrom to form a pair of oppositely oriented centering guides; and wherein the one or more centering profiles is a coaxial pair of oppositely oriented centering profiles configured to receive the pair of oppositely oriented centering guides.
 3. The submersible pumping system as defined in claim 2, wherein the pair of oppositely oriented centering guides comprise conically shaped protrusions each extending from a face of the terminal end of the corresponding motor or driven shaft; and wherein each of the coaxial pair of oppositely oriented centering profiles is profiled with a conically shaped entryway configured to provide centering engagement with the corresponding centering guides of the terminal ends of the respective motor and driven shafts.
 4. The submersible pumping system as defined in claim 2, wherein the respective splined ends of the motor shaft and driven shaft and corresponding centering guides are substantially coaxial within the splined shaft coupling; wherein a diameter of each of the pair of oppositely oriented centering profiles is smaller than a diameter of the terminal end of the respective motor and driven shafts to form respective faces of the terminal ends of the motor and driven shafts; and wherein a first of the pair of oppositely oriented centering profiles comprises at least portions of a recess or bore extending axially into the body of the alignment element through a first of the pair of oppositely oriented faces of the alignment element, and a second of the pair of oppositely oriented centering profiles comprises at least portions of a recess or bore extending axially into the body of the alignment element through a second of the pair of oppositely oriented faces of the alignment element.
 5. The submersible pumping system as defined in claim 4, wherein the face of the terminal end of the motor shaft contacts with the first of the pair of oppositely oriented faces of the alignment element when projecting its respective centering guide into the first of the pair of oppositely oriented centering profiles; and wherein the face of the terminal end of the driven shaft contacts with the second of the pair of oppositely oriented faces of the alignment element when projecting its respective centering guides into the second of the pair of oppositely oriented centering profiles.
 6. The submersible pumping system as defined in claim 1, wherein the alignment element comprises a disk portion, wherein the splined shaft coupling comprises a shoulder formed in the splined shaft coupling, and wherein the substantially cylindrically shaped annular insert is a threaded sleeve secured within the splined shaft coupling, the threaded sleeve positioned in contact with the disk portion of the alignment element, the disk portion being secured between the shoulder and the threaded sleeve.
 7. The submersible pumping sys as defined in claim 1, wherein the splined shaft coupling comprises an annular collar having a first bore positioned to receive the motor shaft and a counter bore positioned to receive the driven shaft, a diameter of the counter bore being larger than a diameter of the first bore to form a shoulder at a juncture therebetween.
 8. A submersible pumping system for pumping wellbore fluid, comprising: a pump motor; a pump; a splined shaft coupling; a motor shaft having a splined end positioned within one end of the splined shaft coupling, the motor shaft having a terminal end; a driven shaft having a splined end positioned within an opposite end of the splined shaft coupling opposite to the motor shaft, the driven shaft having a terminal end, one or both of the terminal ends of the motor shaft and the driven shaft comprising a centering guide individually extending therefrom, the driven shaft being driven by the motor shaft via the splined shaft coupling; and an alignment element landed within the splined shaft coupling, the alignment element having a pair of oppositely oriented faces, an annular shaped body extending therebetween and having a length substantially shorter than a diameter thereof to define a disk shape, and one or more centering profiles each separately extending into the body of the alignment element through a separate one of the pair of opposite faces, the one or more centering profiles coaxially receiving the one or more centering guides correspondingly extending from one or more of the terminal ends of the motor and driven shafts when operably positioned within the shaft coupling.
 9. The submersible pumping system as defined in claim 8, wherein the one or more centering profiles of the alignment element is a coaxial pair of oppositely oriented centering profiles each profiled with a conically shaped entryway; wherein the terminal end of the motor shaft and the terminal end of the driven shaft each separately comprise a centering guide extending therefrom to form a pair of oppositely oriented centering guides each comprising a conically shaped protrusion configured to provide centering engagement with a corresponding one of the pair of oppositely oriented centering profiles; wherein the coaxial pair of oppositely oriented centering profiles coaxially receive the pair of oppositely oriented centering guides; and wherein the terminal ends of the motor shaft and the driven shaft each have complementing surfaces substantially complementing a shape of the corresponding motor shaft-facing and driven shaft-facing surfaces of the alignment element, respectively.
 10. A submersible pumping system for pumping wellbore fluid, comprising: a pump motor; a pump; a splined shaft coupling comprising an annular collar having a first bore and a counter bore, a diameter of the counter bore being larger than a diameter of the first bore to form a shoulder at a juncture therebetween; a motor shaft having a splined end positioned within the first bore of the splined shaft coupling, the motor shaft having a terminal end; a driven shaft having a splined end positioned within the counter bore of the splined shaft coupling opposite to the motor shaft, the driven shaft having a terminal end, one or both of the terminal ends of the motor shaft and the driven shaft comprising a centering guide individually extending therefrom, the driven shaft being driven by the motor shaft via the splined shaft coupling; and an alignment element landed within the splined shaft coupling, the alignment element having: a pair of oppositely oriented faces, a disk-shaped body extending therebetween and having an outer diameter that is larger than the diameter of the first bore at the juncture between the counter bore and the first bore forming the shoulder such that outer peripheries of the disk-shaped body land upon the shoulder, and one or more centering profiles each separately extending into the body of the alignment element through a separate one of the pair of opposite faces, the one or more centering profiles coaxially receiving the one or more centering guides correspondingly extending from one or more of the terminal ends of the motor and driven shafts when operably positioned within the shaft coupling.
 11. The submersible pumping system as defined in claim 10, further comprising an annular insert positioned within the counter bore and in contact with a driven shaft-facing surface of the alignment element to retain the alignment element within the counter bore of the annular collar.
 12. The submersible pumping system as defined in claim 11, wherein the annular insert is a cylindrically shaped annular insert having a bore sized to receive the driven shaft, wherein the splined end of the driven shaft comprises a plurality of elongate square tooth splines, and wherein the cylindrically shaped annular insert comprises a corresponding plurality of elongate female square tooth splines formed along an inner diameter of the annular insert and configured for coupling engagement with the elongate male square tooth splines on the one end of the driven shaft.
 13. An electrical submersible pump (ESP), comprising: a pump; a pump motor; an equalizer or seal section connected between the pump and the pump motor; a motor shaft mechanically affixed to the pump motor, the motor shaft having a splined end portion comprising a plurality of elongate square tooth spines formed thereon, and a terminal end portion comprising a centering guide extending from a face of the terminal end portion, being coaxial with an axis of the motor shaft, and having a base with a diameter being substantially smaller than a diameter of the terminal end portion to form the respective face of the terminal end portion; a driven shaft having a splined end portion comprising a plurality of elongate square tooth spines formed thereon, and a terminal end portion comprising a centering guide extending from a face of the terminal end portion, being coaxial with an axis of the driven shaft, and having a base with a diameter being substantially smaller than a diameter of the terminal end portion to form the respective face of the terminal end portion; a splined shaft coupling assembly rotatingly coupling respective splined ends of the motor shaft and the driven shaft, the respective splined ends of the motor shaft and driven shaft and corresponding centering guides being substantially coaxial within the splined shaft coupling assembly; and an alignment element mounted within portions of the splined shaft coupling assembly, the alignment element having a body, a first centering profile of a pair of oppositely oriented centering profiles extending into a motor shaft-facing side of the alignment element that mates with the centering guide extending from the face of the motor shaft, and a second centering profile of the pair of oppositely oriented centering profiles extending into a driven shaft-facing side of the alignment element that mates with the centering guide extending from the face of the driven shaft, the face of the terminal end portion of the motor shaft contacting with the motor shaft-facing side of the alignment element when projecting its respective centering guide into the first centering profile of the pair of oppositely oriented centering profiles, and the face of the terminal end portions of the driven shaft contacting with the driven shaft-facing side of the alignment element when projecting its respective centering guide into the second centering profile of the pair of oppositely oriented centering profiles.
 14. The ESP as defined in claim 13, wherein the centering profiles and the centering guides are conical and are of substantially same dimensions.
 15. The ESP as defined in claim 13, wherein the alignment element comprises a disk portion, and wherein the splined shaft coupling assembly comprises: an annular collar having an annular shoulder formed therein, the disk portion of the alignment element landing upon the annular collar; and a threaded sleeve secured within the annular collar, the threaded sleeve positioned in contact with the disk portion of the alignment element, the disk portion being secured between the annular shoulder and the threaded sleeve.
 16. The ESP as defined in claim 13, wherein the plurality of elongate square tooth splines on the splined end portions of the motor and driven shafts are male square tooth splines, and wherein the splined shaft assembly comprises: an annular collar; and a substantially cylindrically shaped annular insert positioned within the annular collar, the insert comprising a plurality of elongate female square tooth splines formed along an inner diameter of a bore extending through the insert, the elongate female square tooth splines configured for coupling engagement with the elongate male square tooth splines.
 17. The ESP as defined in claim 13, wherein the splined shaft coupling assembly comprises an annular collar having a first bore positioned to receive the motor shaft and a counter bore positioned to receive the driven shaft, a diameter of the counter bore being substantially different than a diameter of the first bore to form a shoulder at a juncture therebetween; wherein the body of the alignment element comprises a disk-shaped portion, an outer diameter of the disk-shaped portion being larger than an inner diameter of the shoulder, and outer peripheral portions of a first surface of the disk-shaped portion of the alignment element land upon the shoulder; and wherein the splined shaft coupling assembly further comprises an annular insert positioned within the counter bore and in contact with a second surface of the alignment element to retain the alignment element within the counter bore of the annular collar.
 18. The ESP as defined in claim 13, wherein the splined shaft coupling assembly comprises an annular collar having a first bore positioned to receive the motor shaft and a counter bore positioned to receive the driven shaft, a diameter of the counter bore being larger than a diameter of the first bore to form a shoulder at a juncture therebetween; wherein the body of the alignment element comprises a disk-shaped portion, an outer diameter of the disk-shaped portion being larger than an inner diameter of the shoulder, and outer peripheral portions of a motor shaft-facing surface of the disk-shaped portion of the alignment element land upon the shoulder; and wherein the splined shaft coupling assembly further comprises an annular insert positioned within the counter bore and in contact with a driven shaft-facing surface of the alignment element to retain the alignment element within the counter bore of the annular collar.
 19. The ESP as defined in claim 13, further comprising a separator positioned between the equalizer or seal and the pump.
 20. An electrical submersible pump (ESP), comprising: a pump; a pump motor; an equalizer or seal section connected between the pump and the pump motor; a motor shaft mechanically affixed to the pump motor, the motor shaft having a splined end portion comprising a plurality of elongate square tooth spines formed thereon, and a terminal end portion comprising a tapered centering guide extending from a face of the terminal end portion, being coaxial with an axis of the motor shaft, and having a base with a diameter being substantially smaller than a diameter of the terminal end portion to form the respective face of the terminal end portion; a driven shaft having a splined end portion comprising a plurality of elongate square tooth spines formed thereon, and a terminal end portion comprising a tapered centering guide extending from a face of the terminal end portion, being coaxial with an axis of the driven shaft, and having a base with a diameter being substantially smaller than a diameter of the terminal end portion to form the respective face of the terminal end portion; a splined shaft coupling assembly rotatingly coupling respective splined ends of the motor shaft and the driven shaft, the respective splined ends of the motor shaft and driven shaft and corresponding centering guides being substantially coaxial within the splined shaft coupling assembly, the splined shaft coupling assembly comprising an annular collar having a first bore positioned to receive the motor shaft and a counter bore positioned to receive the driven shaft, and an annular insert positioned within the counter bore, a diameter of the counter bore being larger than a diameter of the first bore to form a shoulder at a juncture therebetween; and an alignment element mounted within portions of the splined shaft coupling assembly, the alignment element having a body, a first tapered centering profile extending into a motor shaft-facing side that mates with the tapered centering guide extending from the face of the motor shaft, and a second tapered centering profile extending into an opposite driven shaft-facing side that mates with the tapered centering guide extending from the face of the driven shaft, the body of the alignment element comprising a disk-shaped portion, an outer diameter of the disk-shaped portion being larger than an inner diameter of the shoulder, outer peripheral portions of a motor shaft-facing surface of the disk-shaped portion of the alignment element landing upon the shoulder, the annular insert positioned within the counter bore being in contact with a driven shaft-facing surface of the alignment element to retain the alignment element within the counter bore of the annular collar, the face of the terminal end portion of the motor shaft contacting with the motor shaft-facing side of the alignment element when projecting its respective centering guide into the first tapered centering profile, and the face of the terminal end portions of the driven shaft contacting with the driven shaft-facing side of the alignment element when projecting its respective centering guide into the second tapered centering profile. 